JP6191257B2 - Polarization processing apparatus and piezoelectric element manufacturing method - Google Patents

Description

The present invention relates to a polarization processing apparatus and a method for manufacturing a piezoelectric element.

  Regarding an ink jet recording apparatus and a liquid droplet ejection head used as an image recording apparatus or an image forming apparatus such as a printer, a facsimile machine, and a copying apparatus, a nozzle for ejecting ink droplets, a pressure chamber communicating with the nozzle, and ink in the pressure chamber What has electromechanical conversion elements, such as a piezoelectric element to pressurize, is known. The electromechanical conversion element has, for example, a structure in which an electromechanical conversion film and an upper electrode are stacked on a lower electrode.

  A technique is known in which a polarization process is performed on an element in advance in order to suppress displacement amount deterioration occurring in the piezoelectric element after continuous driving. The piezoelectric crystal subjected to the polarization treatment contains many aggregates of domains in which the directions of polarization are aligned (see FIG. 1).

  Using a corona discharge between a plurality of needle-like electrodes (corona electrodes) and a lower electrode (stage electrode), ions generated by the discharge are used using a grid electrode provided between the needle-like electrodes and the lower electrode. A technique for performing a uniform polarization treatment on a material to be polarized by dispersing (for example, see Patent Document 1).

  The greater the stage electrode voltage (stage voltage), the shorter the polarization treatment time (see FIG. 2). Further, if the stage voltage is not properly applied to the piezoelectric element, the polarization treatment becomes insufficient, and a crack may occur in the electromechanical conversion film (see FIG. 3).

  When changing the layout of the piezoelectric element placed on the stage, it is necessary to change the layout of the stage electrode in order to apply an appropriate polarization process to the piezoelectric element. Manufacturing a new stage each time the layout is changed requires cost and labor.

  In the corona polarization treatment apparatus in Patent Document 1, it is difficult to change the layout of the stage electrodes.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a low-cost polarization processing apparatus in which the layout of the stage electrode can be easily changed.

  The polarization processing apparatus according to the present embodiment is a polarization processing apparatus that performs polarization processing on a piezoelectric element. The polarization processing apparatus includes a plurality of through holes, a stage on which the piezoelectric elements are placed, and a voltage applied to the piezoelectric elements through the through holes. It is necessary to have a stage electrode to be applied, a wire electrode that corona discharges with respect to the stage, and a grid electrode that faces the piezoelectric element and is formed between the wire electrode and the stage electrode.

  According to the present embodiment, it is possible to provide a low-cost polarization processing device in which the layout of the stage electrode can be easily changed.

It is a schematic diagram which illustrates the change of the domain before and behind a polarization process. It is a graph which shows the relationship between a stage voltage and polarization processing time. It is a figure which illustrates the malfunction of a polarization process. It is a figure which illustrates the polarization processing apparatus which concerns on Embodiment 1. FIG. FIG. 3 is a diagram illustrating a stage according to the first embodiment. 4 is a diagram illustrating a stage electrode according to Embodiment 1. FIG. 4 is a diagram illustrating a stage electrode according to Embodiment 1. FIG. 4 is a diagram illustrating a stage electrode according to Embodiment 1. FIG. It is a figure which illustrates the polarization processing apparatus which concerns on Embodiment 1. FIG. 3 is a graph showing a PE hysteresis curve according to the first embodiment. 6 is a diagram illustrating a droplet discharge head according to Embodiment 2. FIG. 6 is a diagram illustrating a piezoelectric element according to a second embodiment. FIG. 6 is a diagram illustrating a droplet discharge head according to Embodiment 2. FIG. 6 is a graph showing a relationship between an angle and diffraction intensity according to the second embodiment. 5 is a perspective view illustrating an ink jet recording apparatus according to Embodiment 3. FIG. 6 is a side view illustrating a mechanism unit of an ink jet recording apparatus according to Embodiment 3. FIG. 1 is a diagram illustrating a piezoelectric element according to Example 1. FIG. 2 is a diagram illustrating a stage electrode according to Example 1. FIG. 2 is a diagram illustrating a stage electrode according to Example 1. FIG. 2 is a diagram illustrating a stage electrode according to Example 1. FIG. 2 is a diagram illustrating a stage electrode according to Example 1. FIG. 2 is a diagram illustrating a stage electrode according to Example 1. FIG. 3 is a graph showing a PE hysteresis curve according to Example 1; 6 is a diagram illustrating a piezoelectric element and a stage electrode according to Example 3. FIG. 6 is a diagram illustrating a stage electrode according to Example 4. FIG. FIG. 10 is a diagram illustrating a piezoelectric element and a stage electrode according to Example 6.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings and tables. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
[Configuration of polarization processing equipment]
The configuration of the polarization processing apparatus according to this embodiment will be described with reference to FIGS.

  The polarization processing apparatus 100 includes a corona electrode (wire electrode) 101, a grid electrode 102, a stage 103, a corona power supply 104, a grid power supply 105, a stage power supply 106, and a stage electrode 107. A piezoelectric element 108 is placed on the stage 103. The layout of the piezoelectric element 108 can be arbitrarily set. The structure of the piezoelectric element 108 is not particularly limited, and may be, for example, a bimorph structure or a unimorph structure.

  The corona electrode 101 is opposed to the stage 103 (stage electrode 107) and is formed via the grid electrode 102 therebetween.

  The grid electrode 102 is formed to face the stage surface (surface on which the piezoelectric element is formed). The grid electrode 102 is formed between the corona electrode 101 and the stage electrode 107.

  Corona voltage is supplied to the corona electrode 101 from a corona power source 104. The grid voltage is supplied to the grid electrode 102 from the grid power source 105. A stage voltage is supplied to the stage electrode 107 from the stage power supply 106.

  It is preferable that a reverse polarity voltage is supplied to the corona electrode 101 and the stage electrode 107. By setting the reverse polarity, the internal voltage difference generated in the piezoelectric element 108 can be increased without changing the state of ions (corona discharge state) generated in the corona electrode 101. As a result, the polarization processing time can be shortened.

  The intensity of the corona discharge in the corona electrode 101 can be appropriately controlled by the magnitude of the corona voltage and the grid voltage, the distance between the stage 103 and the corona electrode 101, the distance between the stage 103 and the grid electrode 102, and the like. Is possible.

  The grid electrode 102 is meshed. For this reason, ions generated around the corona electrode 101 that undergoes corona discharge can be efficiently and uniformly dispersed and can be poured onto the piezoelectric element 108 (stage 103).

  The stage 103 is made of an insulator and includes a plurality of through holes. In order to increase the current density and shorten the polarization treatment time, the shape of the opening in the through hole is preferably a hexagon. Specifically, as shown in FIG. 5 (A), the shape of the top surface has a regular hexagonal shape, and the shape of the cross section is rectangular as shown in FIG. 5 (B). It is preferable to have an adjacent shape.

  Moreover, the shape of the opening part in a through-hole is not limited to a regular hexagon. For example, it may be a hexagon, a circle, an ellipse, a quadrangle, a rectangle, a triangle, or the like.

  It is preferable that a temperature adjustment function is added to the stage 103. The temperature set by the temperature adjusting function is preferably 50 ° C. or higher and 150 ° C. or lower. By performing the polarization process on the stage 103 that has been heated, the polarization process time can be shortened and the efficiency of the polarization process can be increased.

  The stage electrode 107 is formed using the through hole of the stage 103. For example, the stage electrode 107 may be formed as illustrated in FIG. 6A is a top view of the stage electrode 107, and FIG. 6B is a cross-sectional view of the stage electrode 107. In accordance with the layout of the piezoelectric element 108, a plurality of removable rod electrodes 107a are inserted into the through holes, and the lower surface of the rod electrode 107a and the common electrode 107b are brought into contact with each other to form the stage electrode 107. The layout of the stage electrode 107 can be easily changed by arbitrarily selecting the number and position of the rod electrodes 107a to be inserted.

  For example, the stage electrode 107 may be formed as illustrated in FIG. 7A is a top view of the stage electrode 107, and FIG. 7B is a cross-sectional view of the stage electrode 107. An electrode plate 107c is disposed in accordance with the layout of the piezoelectric element 108, and a plurality of removable rod electrodes 107a are inserted into the through holes. The electrode plate 107c and the rod electrode 107a may be bonded with a conductive paste or the like, or may be brought into vacuum contact with each other through a through hole. The stage electrode 107 is formed by bringing the lower surface of the rod electrode 107a into contact with the common electrode 107b. The layout of the stage electrode 107 can be easily changed by arbitrarily selecting the position and shape of the electrode plate 107c to be provided. In the case of FIG. 7, the number of rod electrodes 107a to be inserted can be reduced as compared with the case of FIG.

  In addition, for example, as illustrated in FIGS. 8A and 8B, the insulator rod 110 may be inserted into a through hole into which the rod electrode 107a is not inserted. By inserting the insulator rod 110, the insulation between the rod electrodes 107a and between the electrode plates 107c can be improved, so that the stage electrodes 107 can be formed with high density. Further, the possibility that an unnecessary voltage is applied from the common electrode 107b to the piezoelectric element 108 can be reduced.

  In addition, when the space | interval between through-holes is too large, a difference will arise in a polarization state. Therefore, it is preferable that the space | interval between through-holes is 50 micrometers or more and 1 mm or less.

  As materials for the rod electrode 107a and the electrode plate 107c, a conductive material such as metal is preferably used. For example, copper, platinum, tungsten, stainless steel, aluminum alloy, iridium alloy, gold, graphite and the like can be mentioned.

  Examples of the conductive paste include gold paste and silver paste. The conductive paste is not only used for bonding the rod electrode and the electrode plate, but the conductive paste itself may be filled in the through holes to form the stage electrode. By using the conductive paste as the stage electrode, the shape of the opening in the through hole can be made finer, so that the stage electrode can be formed with high density.

  Since the stage electrode 107 is formed using the through hole of the stage 103, the layout of the stage electrode 107 can be easily changed in accordance with the layout change of the piezoelectric element. That is, it is possible to save the cost and labor of manufacturing a new stage each time the layout is changed and reconnecting electrodes and the like in accordance with the new stage. In addition, since the stage voltage can be accurately applied to the piezoelectric element 108, an appropriate polarization process can be performed to improve the performance of the piezoelectric element 108.

[Principle of polarization processing]
An example of the principle of polarization processing by the polarization processing apparatus 100 will be described with reference to FIG. The polarization processing apparatus 100 performs polarization processing on the piezoelectric element by corona discharge and stage voltage.

  When a corona voltage is applied to the corona electrode 101, molecules 109 in the atmosphere are ionized by corona discharge, and positive ions 109a and negative ions 109b are generated. These ions are applied to the stage 103 through the grid electrode 102 to which mesh processing is applied and a grid voltage is applied.

  The positive ions 109a are injected into the piezoelectric element 108 via the common electrode PAD and the individual electrode PAD (not shown) of the piezoelectric element 108, so that charges of opposite polarity are applied to the upper electrode and the lower electrode of the piezoelectric element 108. accumulate. Further, when a stage voltage is applied from the stage electrode 107 to the piezoelectric element 108 through the through hole, a larger internal voltage difference is generated between the upper electrode and the lower electrode of the piezoelectric element 108, and the piezoelectric element Is polarized.

The voltage necessary for applying a polarization process to the piezoelectric element 108 is proportional to the amount of charge accumulated in the upper electrode or the lower electrode (charge amount Q [C]). The charge amount Q [C] is preferably 1E ⁻⁸ [C] or more, and more preferably 4E ⁻⁸ [C] or more. When the charge amount Q [C] is less than 1E- ⁸ [C], the piezoelectric element cannot be sufficiently polarized.

FIG. 10A is a PE hysteresis loop showing a state before the piezoelectric element 108 is polarized. FIG. 10B is a PE hysteresis loop showing a state after the polarization process is performed on the piezoelectric element 108. The horizontal axis represents applied voltage E (unit: [kV / cm]), and the vertical axis represents polarization P (unit: [μC / cm ² ]).

  First, let Pind be the polarization when the applied voltage E = 0 [kV / cm]. Further, the applied voltage E = 150 [kV / cm], and the polarization when the applied voltage E = 0 [kV / cm] is set to Pr.

  A difference between the polarization Pr and the polarization Pind is defined as a polarizability (Pr−Pind). The state of polarization processing can be determined from the polarizability read from the PE hysteresis loop.

  The polarizability (Pr-Pind) is preferably 10 or less, and more preferably 5 or less. When the polarizability is larger than 10, the displacement amount deterioration after the piezoelectric element 108 is continuously driven becomes large.

<Second Embodiment>
In the present embodiment, a droplet discharge head on which a piezoelectric element subjected to polarization processing by the polarization processing apparatus according to the first embodiment will be described. The piezoelectric element is used as a component part of a droplet discharge head used in an ink jet recording apparatus.

  FIG. 11 is a cross-sectional view illustrating a droplet discharge head 1 using an electromechanical transducer.

  FIG. 12 is a diagram illustrating a piezoelectric element 108 that is a component of the droplet discharge head 1. FIG. 8A is a cross-sectional view of the piezoelectric element 108, and FIG. 8B is a top view of the piezoelectric element 108.

  As shown in FIGS. 11 and 12, the droplet discharge head 1 includes a nozzle plate 10, a pressure chamber substrate 20, a vibration plate 30, a substrate 31, and an electromechanical conversion element 44.

  The nozzle plate 10 is formed with nozzles 11 that eject ink droplets. The nozzle plate 10, the pressure chamber substrate 20, and the vibration plate 30 may be referred to as a pressure chamber 21 (an ink channel, a pressurized liquid chamber, a pressurized chamber, a discharge chamber, a liquid chamber, or the like) that communicates with the nozzle 11. ) Is formed. The diaphragm 30 forms part of the wall surface of the ink flow path.

The electromechanical conversion element 44 includes an upper electrode 41, an electromechanical conversion film 42, a lower electrode 43, an adhesion layer, and the like, and has a function of pressurizing ink in the pressure chamber 21. The adhesion layer is a layer made of, for example, Ti, TiO ₂ , TiN, Ta, Ta ₂ O ₅ , Ta ₃ N _{5, and the} like, and has a function of improving adhesion between the lower electrode 43 and the diaphragm 30. However, the adhesion layer is not an essential component for the piezoelectric element.

  In the electromechanical conversion element 44, when a voltage is applied between the lower electrode 43 and the upper electrode 41, the electromechanical conversion film 42 is mechanically displaced. With the mechanical displacement of the electromechanical conversion film 42, the vibration plate 30 is deformed and displaced, for example, in the lateral direction (d31 direction), and pressurizes the ink in the pressure chamber 21. Thereby, ink droplets can be ejected from the nozzle 11.

  The piezoelectric element 108 includes the substrate 31, the vibration plate 30, the electromechanical conversion element 44, the first insulating protective film 51, the first electrode 52, the second electrode 53, the second insulating protective film 54, and the common. The electrode PAD 57, the individual electrode PAD 58, a lead wiring (not shown), a common electrode wiring, an individual electrode wiring, and the like are included.

  The first insulating protective film 51 has a contact hole 55, and the lower electrode 43 and the first electrode 52 are electrically connected via the contact hole 55, and the upper electrode 41 and the second electrode 52 are connected to each other. The electrode 53 is electrically connected. The second insulating protective film 54 has a contact hole 56, and the first electrode 52 and the common electrode PAD are electrically connected via the contact hole 56, and the second electrode 53 The individual electrode PAD is electrically connected. The second insulating protective film 54 covers the common electrode wiring and the individual electrode wiring and has a function as a protective layer. Since the electrode and the wiring are covered with the protective layer, inexpensive Al, an alloy material containing Al as a main component, or the like can be selected as the electrode material. The common electrode PAD57 is manufactured for common electrode wiring, and the individual electrode PAD58 is manufactured for individual electrode wiring.

  The contact hole 56 is formed around the piezoelectric element 108. The contact holes 55 and 56 can be formed by a combination of photolithography and dry etching. Since the electromechanical conversion element 44 is protected by the first insulating protective film 51 and the second insulating protective film 54, even if the contact hole 56 is formed, the electromechanical conversion element 44 is hardly damaged. .

  The areas of the common electrode PAD57 and the individual electrode PAD58 are preferably 50 μm × 50 μm or more, and more preferably 100 μm × 300 μm or more. As the area of the PAD is increased, the wiring function is improved and an appropriate polarization process can be performed.

  As shown in FIG. 13, a plurality of droplet discharge heads 1 can be arranged in parallel to form the droplet discharge head 2.

  As the material of the substrate 31, it is preferable to use a silicon single crystal substrate, and the thickness is preferably about 100 μm to 600 μm. It is more preferable to use a silicon single crystal substrate whose plane orientation is (100) or (111). The plane orientation is preferably selected in consideration of the speed of etching (for example, anisotropic etching immersed in an alkaline solution such as KOH) when processing the silicon single crystal substrate. It is also preferable to select a silicon single crystal substrate having a plane orientation capable of increasing the crystal arrangement density while maintaining the rigidity of the substrate.

As the material of the diaphragm 30, a material having a certain degree of strength is preferably used, and examples thereof include silicon (Si), silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), and the like. Further, it may be selected in consideration of the thermal expansion coefficient. Specifically, it is preferable to use a material having a thermal expansion coefficient satisfying a range of 5 × 10 ⁻⁶ [1 / K] to 10 × 10 ⁻⁶ [1 / K], and 7 × 10 ⁻⁶ [1 / K. ] To 9 × 10 ⁻⁶ [1 / K] is more preferably used. Examples of these materials include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof.

  The diaphragm 30 can be formed by a method such as a CVD method, a sputtering method, or a sol-gel method. The film thickness of the diaphragm 30 is preferably about 0.1 μm to 10 μm, and more preferably about 0.5 μm to 3 μm. Note that the surface of the vibration plate 30 may be insulated by, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film having a thickness of about several hundreds nm to several μm, or a film in which these films are stacked. .

The adhesion layer is preferably formed of a material such as Ti, Ta, Ir, or Ru by a thermal oxidation method using an RTA apparatus after sputtering film formation. For example, after Ti is sputtered as an adhesion layer, a Ti film is thermally oxidized in an oxygen atmosphere using an RTA apparatus under conditions of a film forming temperature of 650 ° C. to 800 ° C. and a film forming time of 1 minute to 30 minutes. By doing so, a TiO ₂ film may be formed. The thickness of the adhesion layer is preferably about 10 nm to 50 nm, and more preferably about 15 nm to 30 nm.

  The lower electrode 43 is preferably composed of a laminated film of a metal film and an oxide film.

  As the metal material of the lower electrode 43, ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt) having high heat resistance and low reactivity. Platinum group metals such as these, and alloy materials containing these platinum group metals can be used. The metal film can be formed using a vacuum film formation method such as a sputtering method or a vacuum evaporation method. The thickness of the metal film is preferably about 80 nm to 200 nm, and more preferably about 100 nm to 150 nm. If it is thinner than 80 nm, the ejection reliability of the droplet ejection head 2 is lowered. In addition, when the thickness is greater than 200 nm, the cost increases, the surface roughness of the metal film increases, and the crystal orientation of the oxide film and electromechanical conversion film formed on the metal film is adversely affected. .

As the oxide material of the lower electrode 43, a conductive oxide material is preferably used. Specifically, it is described by the chemical formula Sr _(x) A _(1-x) Ru _{(y (1-y))} , and A = Ba, Ca, B = Co, Ni, (y = 0 to 0.5) Etc. can be used. In addition, there is a composite oxide described by the chemical formula ABO ₃ and having A = Sr, Ba, Ca, La, B = Ru, Co, Ni as main components, and SrRuO ₃ , CaRuO ₃ , and solid solutions thereof ( In addition to Sr _1-x Ca _x ) O ₃ , LaNiO ₃ and SrCoO ₃ , and further, (La, Sr) (Ni _1-y Co _y ) O ₃ (y = 1 may be used), which is a solid solution thereof, may be mentioned. . Other oxide materials include IrO ₂ and RuO ₂ . In particular, SRO (strontium ruthenate) is preferably used.

  The oxide film can be formed using, for example, a sputtering method or the like. The film formation temperature is preferably adjusted as appropriate in consideration of surface roughness and crystal orientation. The film formation temperature is preferably 500 ° C. or more and 700 ° C. or less, and more preferably 520 ° C. or more and 600 or less. Further, the surface roughness is preferably about 4 nm to 15 nm, and more preferably about 6 nm to 10 nm.

  The thickness of the oxide film is preferably about 40 nm to 150 nm, and more preferably about 50 nm to 80 nm. When the film thickness satisfies this range, the displacement deterioration of the electromechanical conversion film after continuous driving can be suppressed, and the oxide film sufficiently functions as a stop etching layer for suppressing overetching of the electromechanical conversion film. be able to.

When SRO is used as the oxide material, the Sr / Ru composition ratio after the film formation is preferably 0.82 or more and 1.22 or less. If Sr / Ru does not satisfy this range, the SRO film has a large specific resistance, and sufficient conductivity as an electrode cannot be obtained. The specific resistance is preferably 5 × 10 ⁻³ Ω · cm or less, and more preferably 1 × 10 ⁻³ Ω · cm or less. As the crystal orientation of the SRO film, it is preferable that the (111) plane has a high orientation rate. When the orientation ratio of the (111) plane is high, a peak of diffraction intensity can be confirmed near Psi = 35 ° in the measurement result by XRD (X-ray-diffractive) measurement fixed at 2θ = 32 ° (see FIG. 14). ).

As a material of the electromechanical conversion film 42, for example, PZT can be used. PZT is a solid solution of lead zirconate (PbZrO ₃ ) and lead titanate (PbTiO ₃ ). For example, the ratio of PbZrO ₃ and PbTiO ₃ is 53:47, and the chemical formula indicates Pb (Zr _0.53 , Ti _0.47 ) O ₃ , PZT generally indicated as PZT (53/47), etc. Can be used. The characteristics of PZT vary depending on the ratio of PbZrO ₃ and PbTiO ₃ .

When PZT is used as the electromechanical conversion film 42, lead acetate trihydrate, zirconium alkoxide compound, or titanium alkoxide compound may be used as a starting material. These starting materials are dissolved in a common solvent to produce a PZT precursor sol-gel solution. The mixing amount of lead acetate trihydrate, zirconium alkoxide compound, and titanium alkoxide compound can be appropriately selected by those skilled in the art according to the desired composition of PZT (ratio of PbZrO ₃ and PbTiO ₃ ). Note that the metal alkoxide compound is easily decomposed by moisture in the atmosphere. Therefore, acetylacetone, acetic acid, diethanolamine or the like may be added as a stabilizer to the PZT precursor sol-gel solution.

  As a material of the electromechanical conversion film 42, for example, barium titanate or the like may be used. In this case, a barium titanate precursor sol-gel solution can be prepared by using a barium alkoxide compound and a titanium alkoxide compound as starting materials and dissolving them in a common solvent. Further, for example, a solid solution of barium titanate and bismuth perovskite may be used.

These materials are described by the general formula _{ABO 3, A = Pb, Ba} , Sr, Bi B = Ti, Zr, Sn, Ni, Zn, Mg, composite oxide corresponds mainly composed of Nb. The specific description is expressed as (Pb _1-x , Ba) (Zr, Ti) O ₃ , (Pb _1-x , Sr) (Zr, Ti) O ₃ , which is the same as Pb of the A site. This is a case where the part Ba or Sr is substituted. Such substitution is possible with a divalent element, and the effect thereof has an effect of reducing characteristic deterioration due to evaporation of lead during heat treatment.

  The electromechanical conversion film 42 is formed by, for example, using a solution coating method such as a sputtering method or a sol-gel method to form a precursor coating on the lower electrode, and solvent drying, thermal decomposition, It can be formed by heat treatment such as crystallization. In general, since transformation from a precursor coating to a crystallized film involves volume shrinkage, a precursor sol-gel is formed so that a film thickness of 100 nm or less is obtained in one step in order to obtain a crack-free film. It is preferable to adjust the concentration of the solution.

  The thickness of the electromechanical conversion film 42 is preferably about 0.5 μm to 5 μm, and more preferably about 1 μm to 2 μm. If it is smaller than this range, a sufficient amount of displacement cannot be obtained. If it is larger than this range, the number of steps increases and the process time becomes longer.

  The relative dielectric constant of the electromechanical conversion film 42 is preferably 600 or more and 2000 or less, and more preferably 200 or more and 1600 or less.

  Similar to the lower electrode 43, the upper electrode 41 is preferably composed of a laminated film of a metal film and an oxide film. As the metal material and the oxide material, the same material as that of the lower electrode 43 can be used. The thickness of the metal film is preferably about 30 nm to 200 nm, and more preferably about 50 nm to 120 nm. The thickness of the oxide film is preferably about 20 nm to 80 nm, and more preferably about 40 nm to 60 nm.

As the material of the first insulating protective film 51, it is preferable to use a dense inorganic material or the like that is difficult to transmit moisture in the atmosphere. By using such a material, it is possible to prevent damage to the electromechanical conversion element 44 during the film forming process and the etching process. Further, as the material of the first insulating protective film 51, it is preferable to use a thin film material having high protection performance. Specific examples include oxides, nitrides, carbides, and the like. Further, as the material of the first insulating protective film 51, it is preferable to use a material having high adhesion to an electrode, an electromechanical conversion film, a substrate, a vibration plate, or the like. _{Specifically, Al 2 O 3, ZrO 2} , Y 2 O 3, Ta 2 O 3, the oxide material of the TiO ₂ and the like. By using these oxide materials, it is possible to suppress damage during the process by the ALD (Atomic Layer Deposition) method and to produce the first insulating protective film 51 having a very high film density.

  The first insulating protective film 51 can be formed by, for example, a vapor deposition method, an ALD method, or the like.

  The film thickness of the first insulating protective film 51 needs to be thick enough to ensure the function as a protective layer of the piezoelectric element 108 and thin enough not to hinder the mechanical displacement of the diaphragm 30. There is a need. For this reason, the film thickness is preferably about 20 nm to 100 nm. When the film thickness is greater than 100 nm, the mechanical displacement of the diaphragm 30 is hindered, and the discharge efficiency of the droplet discharge head 1 is deteriorated. On the other hand, when the film thickness is thinner than 20 nm, the performance of the piezoelectric element 108 deteriorates.

  The first insulating protective film 51 may have a two-layer structure. In this case, it is preferable that the thickness of the first insulating protective film is larger than the thickness of the second insulating protective film. The thickness of the first insulating protective film is preferably about 20 nm or more. Further, it is preferable that the thickness of the second insulating protective film is increased to such an extent that dielectric breakdown is not caused by an electric field applied to the lower electrode 43, the individual electrode PAD58, and the like. That is, the thickness of the second insulating protective film is preferably about 200 nm or more, and more preferably about 500 nm or more.

  As a material for the second-layer insulating protective film, an oxide, a nitride, a carbide, a composite compound thereof, or the like can be used. In particular, it is preferable to use silicon oxide.

  A known film formation method can be used for the second insulating protective film, and examples thereof include a CVD method and a sputtering method. In consideration of a step generated in a portion where an electrode is formed, it is more preferable to use a CVD method capable of isotropic film formation.

As a material of the second insulating protective film 54, an inorganic material or an organic material having low moisture permeability can be used. Even when the film thickness is thin, it is more preferable to use an inorganic material having a sufficient wiring protection function. Specific examples of the inorganic material include oxides, nitrides, and carbides. In particular, it is preferable to use Si ₃ N ₄ . Specific examples of the organic material include polyimide, acrylic resin, and urethane resin.

  The thickness of the second insulating protective film 54 is preferably about 200 nm or more, and more preferably about 500 nm or more.

  Note that if the thickness of the second insulating protective film 54 is too thin, it cannot function as a protective layer sufficiently, so that disconnection occurs due to corrosion of the wiring material, and the discharge reliability of the droplet discharge head 1 is improved. descend. If it is too thick, mechanical displacement of the diaphragm 31 will be hindered.

  As a material of the first electrode 52 and the second electrode 53, a metal or the like can be used. Specifically, copper (Cu), aluminum (Al), gold (Au), platinum (Pt), iridium (Ir) and other metals, alloy materials containing silver (Ag), and aluminum (Al) as the main component An alloy material or the like can be used.

  The first electrode 52 and the second electrode 53 can be formed using, for example, a sputtering method, a spin coating method, or the like.

  The film thicknesses of the first electrode 52 and the second electrode 53 are preferably about 0.1 μm to 20 μm, and more preferably about 0.2 μm to 10 μm. If the film thickness is too thin, the resistances of the first electrode 52 and the second electrode 53 increase, and a sufficient current cannot flow, so that the ejection reliability of the droplet ejection head 1 decreases. On the other hand, if the film thickness is too thick, the film formation time becomes long.

  The contact resistance of the first electrode 52 at a contact hole (for example, 10 μm × 10 μm) 56 is preferably 10Ω or less, and more preferably 5Ω or less.

  The contact resistance of the second electrode 53 at a contact hole (for example, 10 μm × 10 μm) 56 is preferably 1Ω or less, and more preferably 0.5Ω or less.

  By using the piezoelectric element 108 that has been polarized by the polarization processing apparatus 100 for the droplet ejection head 1 and the droplet ejection head 2, ejection reliability of the droplet ejection head can be improved.

<Third Embodiment>
In the present embodiment, an example of an ink jet recording apparatus equipped with a droplet discharge head 1 (see FIG. 11) is shown. FIG. 15 is a perspective view illustrating an ink jet recording apparatus. FIG. 16 is a side view illustrating the mechanism unit of the ink jet recording apparatus.

  Referring to FIGS. 15 and 16, the inkjet recording apparatus 4 is an inkjet that is an embodiment of a droplet 93 that is movable in the main scanning direction inside the recording apparatus main body 81 and the droplet discharge head 1 mounted on the carriage 93. A printing mechanism 82 including an ink cartridge 95 that supplies ink to the recording head 94 and the ink jet recording head 94 is accommodated.

  A paper feed cassette 84 (or a paper feed tray) on which a large number of sheets 83 can be stacked can be detachably attached to the lower portion of the recording apparatus main body 81. Further, the manual feed tray 85 for manually feeding the paper 83 can be turned over. The paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and after a required image is recorded by the printing mechanism unit 82, the paper is discharged to a paper discharge tray 86 mounted on the rear side.

  The printing mechanism 82 holds the carriage 93 slidably in the main scanning direction with a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). The carriage 93 has an inkjet recording head 94 that ejects ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), and a plurality of ink ejection ports (nozzles) in the main scanning direction. They are arranged in the intersecting direction and mounted with the ink droplet ejection direction facing downward. Further, the carriage 93 is mounted with replaceable ink cartridges 95 for supplying ink of each color to the ink jet recording head 94.

  The ink cartridge 95 has an air port (not shown) that communicates with the atmosphere above, an air port (not shown) that supplies ink to the ink jet recording head 94 below, and a porous body (not shown) filled with ink inside. ing. The ink supplied to the inkjet recording head 94 is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the respective color heads are used here as the ink jet recording head 94, one head having nozzles for ejecting ink droplets of each color may be used.

  The carriage 93 is slidably fitted to the main guide rod 91 on the downstream side in the paper conveyance direction, and is slidably mounted on the sub guide rod 92 on the upstream side in the paper conveyance direction. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a driving pulley 98 and a driven pulley 99 that are rotationally driven by the main scanning motor 97, so that the main scanning motor 97 is forward / reverse. The carriage 93 is reciprocated by the rotation. The timing belt 100 is fixed to the carriage 93.

  Further, the ink jet recording apparatus 4 reverses and feeds the paper feed roller 101 for separating and feeding the paper 83 from the paper feed cassette 84, the friction pad 102, the guide member 103 for guiding the paper 83, and the fed paper 83. A conveyance roller 104, a conveyance roller 105 that is pressed against the circumferential surface of the conveyance roller 104, and a leading end roller 106 that defines a feeding angle of the sheet 83 from the conveyance roller 104 are provided. Thus, the paper 83 set in the paper feed cassette 84 is conveyed to the lower side of the ink jet recording head 94. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

  The printing receiving member 109 which is a paper guide member guides the paper 83 sent out from the conveying roller 104 corresponding to the movement range of the carriage 93 in the main scanning direction on the lower side of the ink jet recording head 94. On the downstream side of the printing receiving member 109 in the sheet conveyance direction, a conveyance roller 111 and a spur 112 that are rotationally driven to send out the sheet 83 in the sheet discharge direction are provided. Further, a paper discharge roller 113 and a spur 114 for sending the paper 83 to the paper discharge tray 86, and guide members 115 and 116 for forming a paper discharge path are provided.

  During image recording, the inkjet recording head 94 is driven in accordance with the image signal while moving the carriage 93, thereby ejecting ink onto the stopped paper 83 to record one line and transporting the paper 83 by a predetermined amount. After that, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing end of the paper 83 reaches the recording area, the recording operation is terminated and the paper 83 is discharged.

  A recovery device 117 for recovering defective ejection of the inkjet recording head 94 is provided at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit. The carriage 93 is moved to the recovery device 117 side during printing standby, and the ink jet recording head 94 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant, and stable ejection performance is maintained.

  When ejection failure occurs, the ejection port of the ink jet recording head 94 is sealed with a capping unit, and bubbles and the like are sucked out from the ejection port with the suction unit through the tube. Also, ink or dust adhering to the ejection port surface is removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, since the inkjet recording head 94 which is an embodiment of the droplet discharge head 1 manufactured by the thin film manufacturing apparatus 3 is mounted in the inkjet recording apparatus 4, ink droplet discharge failure due to vibration plate drive failure occurs. In addition, since stable ink droplet ejection characteristics can be obtained, image quality can be improved.

<Example 1>
In this example, five different stage electrodes were produced. Each stage electrode was set to Sample 1 to Sample 5. Even if the shape of the stage electrode was changed, it was evaluated whether an appropriate polarization treatment was performed on the piezoelectric element. The layout of the stage electrodes was matched to the layout of the piezoelectric elements shown in FIG. The piezoelectric element and the stage were fixed with positioning pins installed in the through holes. In this case, since it is not necessary to separately provide a piezoelectric element fixing function on the stage, the piezoelectric element can be mounted relatively freely on the stage.

[Sample 1]
Sample 1 is shown in FIG. 18A is a top view and FIG. 18B is a cross-sectional view. A stage in which the shape of the opening of the through hole is a regular hexagon was used.

  In accordance with the layout of the piezoelectric element shown in FIG. 17, a plurality of removable metal rods A are inserted into the through holes, and the lower surface of the metal rod A and the common electrode B formed on one surface are brought into contact with each other. An electrode was formed. As a material for the metal rod A, copper was used. As a material for the common electrode B, copper was used.

[Sample 2]
Sample 2 is shown in FIG. FIG. 19A is a top view and FIG. 19B is a cross-sectional view. A stage in which the shape of the opening of the through hole is a regular hexagon was used.

  A plurality of removable metal rods A were inserted into the through holes. Compared to sample 1, the number of metal rods A to be inserted was reduced. Further, an electrode plate C was disposed in accordance with the layout of the piezoelectric element shown in FIG. 17, and the metal rod A and the electrode plate C were bonded with a conductive paste. A stage electrode was formed by bringing the lower surface of the metal rod A into contact with the common electrode B formed on one surface. As the material of the electrode plate C, copper was used.

[Sample 3]
Sample 3 is shown in FIG. 20A is a top view and FIG. 20B is a cross-sectional view. A stage in which the shape of the opening of the through hole is a regular hexagon was used.

  A plurality of removable metal rods A were inserted into the through holes. Compared to sample 1, the number of metal rods A to be inserted was reduced. Further, an electrode plate C was disposed in accordance with the layout of the piezoelectric element shown in FIG. 17, and the metal rod A and the electrode plate C were bonded with a conductive paste. Further, the stage electrode was formed by bringing the lower surface of the metal rod A into contact with the common electrode B (see FIG. 20C) formed in multiple rows for each row of through holes.

[Sample 4]
Sample 4 is shown in FIG. FIG. 21A is a top view, and FIG. 21B is a cross-sectional view. A stage in which the shape of the opening of the through hole is a regular hexagon was used.

  A plurality of rods D with metal rods covered with an insulator were inserted into the through holes. A regular hexagonal electrode cable (not shown) was attached to the upper end of the rod D, and an electrode cable E was attached to the lower end of the rod D. Further, in accordance with the layout of the piezoelectric element shown in FIG. 17, an electrode plate C is disposed, and a regular hexagonal electrode cable and the electrode plate C are bonded with a conductive paste to form a stage electrode.

[Sample 5]
Sample 5 is shown in FIG. 22A is a top view and FIG. 22B is a cross-sectional view. A stage in which the shape of the opening of the through hole was circular was used.

  A plurality of rods D with metal rods covered with an insulator were inserted into the through holes. A circular electrode cable (not shown) was attached to the upper end of the rod D, and an electrode cable E was attached to the lower end of the rod D. Further, in accordance with the layout of the piezoelectric element shown in FIG. 17, an electrode plate C is disposed, and a regular hexagonal electrode cable and the electrode plate C are bonded with a conductive paste to form a stage electrode.

[Production of piezoelectric elements]
Next, a piezoelectric element to be placed on the stage was produced.

  First, a thermal oxide film (film thickness: 1 μm) was formed on a 6-inch silicon wafer. In this example, a single crystal silicon wafer having a (100) plane orientation was mainly used.

  Next, a titanium film (film thickness: 30 nm) was formed as an adhesion layer using a sputtering apparatus. The film forming temperature was 350 ° C. Note that the sputtering apparatus is provided with a plurality of targets for one chamber.

  Next, thermal oxidation was performed on the titanium film at 750 ° C. using an RTA (Rapid Thermal Annealing) apparatus.

  Next, as a first electrode, a platinum film (film thickness: 100 nm) and an SRO film (film thickness: 50 nm) were formed using a sputtering apparatus. The film forming temperature was 550 ° C.

  Next, a starting material for preparing a PZT precursor solution was prepared. As starting materials, lead acetate trihydrate, isopropoxide titanium and isopropoxide zirconium were used. A solution of lead acetate crystal water dissolved in methoxyethanol was dehydrated.

These starting materials were weighed so that the lead amount would be excessive with respect to the stoichiometric composition of Pb (Zr _0.53 , Ti _0.47 ) O ₃ . This is to prevent so-called crystallinity degradation due to lead loss during heat treatment.

  Next, an alcohol exchange reaction and an esterification reaction were allowed to proceed with a solution in which isopropoxide titanium and isopropoxide zirconium were dissolved in methoxyethanol.

  Next, these solutions were mixed to prepare a PZT precursor solution. The PZT precursor solution was 0.5 mol / l. In the PZT precursor solution, the composition ratios of Pb, Zr, and Ti were adjusted to be Pb: Zr: Ti = 114: 53: 47.

  Next, as an electromechanical conversion film, a PZT precursor solution was formed by spin coating.

  Next, the silicon wafer was placed on a hot plate, and a first heat treatment was performed from the lower surface of the silicon wafer. The temperature increase rate was 10 ° C./min, and the temperature was increased from room temperature to 120 ° C. Even after the temperature of the hot plate reached 120 ° C., heat treatment was performed until the solution was dried. Next, a second heat treatment was performed. By performing the heat treatment at 500 ° C., the organic substance contained in the precursor coating film was thermally decomposed. Next, third heat treatment (crystallization treatment) was performed. The heat-treated precursor coating film was crystallized by performing a rapid heat treatment at 750 ° C. using an RTA apparatus. The film thickness of the crystallized precursor coating film was 240 nm.

  Next, the process of film formation of PZT precursor solution and heat treatment was repeated 8 times. As a result, a PZT film having a thickness of about 2 μm was obtained.

  Next, as a second electrode, an SRO film (film thickness: 40 nm) and a platinum film (film thickness: 125 nm) were formed using a sputtering apparatus. The film forming temperature was 550 ° C.

  Next, a photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. was formed by spin coating, and a resist pattern was formed by a known photolithography method (see FIG. ○). Based on the resist pattern, dry etching was performed using an ICP etching apparatus (manufactured by Samco).

Next, an Al ₂ O ₃ film (film thickness: 50 nm) was formed as the first insulating protective film by ALD. For Al, TMA (Sigma Aldrich) and for O, O ₃ generated by an ozone generator was alternately stacked to form an Al ₂ O ₃ film.

  Next, the first insulating protective film was etched to form contact holes.

  Next, an Al film (thickness: 2 μm) was formed as a third electrode and a fourth electrode by a sputtering apparatus, and the Al film was etched.

Next, an Si ₃ N ₄ film (thickness: 500 nm) was formed as a second insulating protective film by a plasma CVD (Chemical Vapor Deposition) method.

  Next, the second insulating protective film was etched to form contact holes.

Thereby, the piezoelectric element was able to be produced. The layout of the piezoelectric elements was adjusted to the layout shown in FIG.
[Polarization treatment]
Using the stage electrodes of Samples 1 to 5, polarization processing was performed on the piezoelectric elements manufactured by the polarization processing apparatus. As the corona electrode, a tungsten wire having a wire diameter of 50 μm was used. Table 1 shows the polarization treatment conditions.

In Samples 1, 2, 4, and 5, the stage voltage where the piezoelectric element was not placed was floated, and in Sample 3, the stage voltage where the piezoelectric element was not placed was 50V. The other polarization treatment conditions are all equal, the corona voltage is 8.5 kV, the grid voltage is 2.5 kV, the distance between the corona electrode and the grid electrode is 4 mm, the distance between the grid electrode and the stage is 4 mm, The processing temperature (stage substrate heating temperature) was room temperature, and the stage voltage of the portion where the piezoelectric element was placed was −100V.

  The polarization treatment time was the time required for the polarizability (Pr-Pind) to reach 3.0 when the corona discharge treatment was performed. In samples 1, 2, 4, and 5, the polarization processing time was 20 [sec], and in sample 3, the polarization processing time was 15 [sec].

  Therefore, it was found that the polarization processing time can be shortened by applying stage voltages having opposite polarities to the part where the piezoelectric element is not placed and the part where the piezoelectric element is placed.

FIG. 23 is a PE hysteresis curve of Samples 1 to 5. The remanent polarization was 20 [μC / cm ² ], the coercive voltage was 30 [kV / cm], and it was found that the remanent polarization had the same characteristics as a normal ceramic sintered body. In addition, the electromechanical conversion ability was calculated by measuring the amount of deformation due to voltage application (150 kV / cm) with a laser Doppler vibrometer and fitting by simulation. The piezoelectric constant d31 was 150 [pm / V]. Therefore, it was found that the piezoelectric constant was equivalent to that of an ordinary ceramic sintered body. This value is a characteristic value that can be sufficiently designed as a piezoelectric element used in a droplet discharge head. Even after the piezoelectric element was continuously driven 1 × 10 ¹⁰ times, the characteristic value equivalent to that of an ordinary ceramic sintered body was maintained.

  Therefore, it has been found that even if the shape of the stage electrode is changed, the piezoelectric element can be appropriately polarized.

  In addition, when functional ink whose viscosity was adjusted to 5 cp was used and the applied voltage of -10 V to -30 V was applied with a simple Pull waveform, the discharge status from the droplet discharge head was confirmed. All nozzle holes Thus, it was confirmed that the liquid droplet (functional ink) was stably ejected.

  Accordingly, it has been found that a droplet discharge head formed using a piezoelectric element subjected to appropriate polarization processing has high discharge reliability.

<Example 2>
In this example, Sample 6 was produced. The shape of the stage electrode of Sample 5 was the same, and the bonding method between the regular hexagonal electrode cable and the electrode plate C was changed.

  The through hole was provided with an electrode plate adsorption function, and the hexagonal electrode cable and the electrode plate C were fixed in vacuum through the through hole.

  Also, the piezoelectric element and the stage were fixed in close contact with each other through a through hole. By providing the through-hole with a piezoelectric element adsorption function, damage to the piezoelectric element can be suppressed, and there is no need to provide a separate piezoelectric element fixing function on the stage, thus increasing the degree of freedom of layout of the piezoelectric element. Can do.

  Table 2 shows the polarization treatment conditions.

In Samples 5 and 6, the polarization treatment conditions are all equal, the corona voltage is 8.5 kV, the grid voltage is 2.5 kV, the distance between the corona electrode and the grid electrode is 4 mm, and the distance between the grid electrode and the stage is The distance was 4 mm, the processing temperature was room temperature, the stage voltage where the piezoelectric element was placed was -100 V, and the stage voltage where the piezoelectric element was not placed was float.

  The polarization treatment time was the time required for the polarizability (Pr-Pind) to reach 3.0 when the corona discharge treatment was performed. In samples 5 and 6, the polarization treatment time was 20 [sec].

  Therefore, it was found that the piezoelectric element can be appropriately polarized regardless of whether the hexagonal electrode cable and the electrode plate C are bonded using a conductive paste or are vacuum-adhered and fixed.

<Example 3>
In this example, Sample 7 was produced. Although the shape was the same as the stage electrode of Sample 5, no stage voltage was applied to some of the stage electrodes. The polarization state of the piezoelectric element was compared between the piezoelectric element placed on the part where the stage voltage was not applied and the piezoelectric element placed on the part where the stage voltage was applied.

  As shown in FIG. 24, a piezoelectric element placed on a portion where no stage voltage was applied was used as a monitor element.

  No polarization occurred in the monitor element, and polarization occurred in the piezoelectric element placed on the portion to which the stage voltage was applied. Therefore, it has been found that the polarization treatment becomes insufficient unless a stage voltage is applied to the stage electrode where the piezoelectric element is placed. That is, it is suggested that the stage voltage greatly contributes to the polarization state of the piezoelectric element.

<Example 4>
In this example, Sample 8 was produced. Sample 8 is shown in FIG. FIG. 25A is a top view and FIG. 25B is a cross-sectional view. A stage in which the shape of the opening of the through hole was circular was used.

  A plurality of rods D with metal rods covered with an insulator were inserted into the through holes. A circular electrode cable (not shown) was attached to the upper end of the rod D, and an electrode cable E was attached to the lower end of the rod D. In addition, an electrode plate C was disposed in accordance with the layout of the piezoelectric element shown in FIG. 17, and the circular electrode cable and the electrode plate C were bonded with a conductive paste. In addition, an electrode plate F was disposed on a portion where the piezoelectric element was not placed, and a circular electrode cable and an electrode plate C were bonded with a conductive paste to form a stage electrode. Table 3 shows the polarization treatment conditions.

In sample 5, the stage voltage of the portion where the piezoelectric element is not placed is floated, and in sample 8, the stage voltage of the portion where the piezoelectric element is not placed is 50V. The other polarization treatment conditions are all equal, the corona voltage is 8.5 kV, the grid voltage is 2.5 kV, the distance between the corona electrode and the grid electrode is 4 mm, the distance between the grid electrode and the stage is 4 mm, The processing temperature was room temperature, and the stage voltage of the portion where the piezoelectric element was placed was −100V.

  The polarization treatment time was the time required for the polarizability (Pr-Pind) to reach 3.0 when the corona discharge treatment was performed. In sample 5, the polarization treatment time was 20 [sec], and in sample 3, the polarization treatment time was 15 [sec].

  Therefore, the polarization processing time can be shortened by applying stage voltages having opposite polarities to the part where the piezoelectric element is not placed and the part where the piezoelectric element is placed through the electrode plate F, respectively. I understood.

<Example 5>
In this example, using the sample 1, the polarization treatment conditions were changed and each piezoelectric element was subjected to polarization treatment. Table 4 shows the polarization treatment conditions.

The treatment temperatures were room temperature and 80 ° C., respectively. The other polarization treatment conditions are all equal, the corona voltage is 8.5 kV, the grid voltage is 2.5 kV, the distance between the corona electrode and the grid electrode is 4 mm, the distance between the grid electrode and the stage is 4 mm, The stage voltage of the portion where the piezoelectric element is placed is -100 V, and the stage voltage of the portion where the piezoelectric element is not placed is float.

  The polarization treatment time was the time required for the polarizability (Pr-Pind) to reach 3.0 when the corona discharge treatment was performed. The polarization treatment time at a treatment temperature of room temperature was 20 [sec], and the polarization treatment time at a treatment temperature of 80 ° C. was 18 [sec].

  Therefore, it was found that the polarization treatment time can be shortened by increasing the treatment temperature. It is suggested that the mechanical and electrical changes of the piezoelectric element can be promoted and the efficiency of the polarization treatment can be improved.

<Example 6>
In this embodiment, the layout of the piezoelectric element is changed. In accordance with the layout change, the stage electrode was changed to produce Sample 9 and Sample 10. Using the stage electrodes of Sample 9 and Sample 10, each piezoelectric element was subjected to polarization treatment. Sample 1 and sample 9 were compared in polarization state. FIG. 26A shows a layout X of the piezoelectric elements and a cross-sectional view of the sample 9. FIG. 26B shows a layout Y of the piezoelectric element and a cross-sectional view of the sample 10.

  In Sample 9 and Sample 10, a stage in which the shape of the opening of the through hole is a regular hexagon is used.

A plurality of removable metal rods A were inserted into the through holes. Since the layout Y of the piezoelectric elements is higher than that of the layout X of the piezoelectric elements, the number of metal rods A inserted in the sample 10 is larger than the number of metal rods A inserted in the sample 9.
In addition, the electrode plates C were respectively arranged in accordance with the layouts X and Y of the piezoelectric elements, and the metal rod A and the electrode plate C were bonded with a conductive paste. Further, the sample 9 and the sample 10 were formed by bringing the lower surface of the metal rod A into contact with the common electrode B formed on one surface.

  Table 5 shows the polarization treatment conditions.

The polarization treatment conditions are all equal, the corona voltage is 8.5 kV, the grid voltage is 2.5 kV, the distance between the corona electrode and the grid electrode is 4 mm, the distance between the grid electrode and the stage is 4 mm, and the processing temperature. Is room temperature, the stage voltage of the portion where the piezoelectric element is placed is −100 V, and the stage voltage of the portion where the piezoelectric element is not placed is float.

  The polarization treatment time was the time required for the polarizability (Pr-Pind) to reach 3.0 when the corona discharge treatment was performed. The polarization treatment time was 20 [sec] and was equal.

  Therefore, it has been found that even if the layout of the stage electrode is changed in accordance with the change of the layout of the piezoelectric element, an appropriate polarization process can be applied to each piezoelectric element. By using the through-holes provided in the stage, it is possible to change the layout of the stage electrodes relatively easily, which suggests that a low-cost polarization processing apparatus can be realized.

<Comparative example>
As a comparative example, in Sample 1, the piezoelectric element was subjected to polarization treatment without applying a voltage to the stage electrode. Table 6 shows the polarization treatment conditions.

The polarization treatment conditions are as follows: the corona voltage is 8.5 kV, the grid voltage is 2.5 kV, the distance between the corona electrode and the grid electrode is 4 mm, the distance between the grid electrode and the stage is 4 mm, the processing temperature is room temperature, the stage The voltage was GND (grounded).

  The polarization treatment time was the time required for the polarizability (Pr-Pind) to reach 3.0 when the corona discharge treatment was performed. The polarization treatment time was 30 [sec], which was longer than that of the example. It was found that unless the stage voltage was applied to the stage electrode, an appropriate polarization treatment was not applied to the piezoelectric element. That is, it has been found that it is necessary not only to apply a voltage to the corona electrode and the grid electrode, but also to apply an appropriate stage voltage to the stage electrode.

  From the results of the examples and comparative examples, in the polarization processing apparatus, even if the layout of the stage electrode is changed or the shape of the stage electrode is changed using the through holes provided in the stage, the polarization state of the piezoelectric element is changed. It was found that there was no adverse effect. It was found that by appropriately applying a stage voltage from the stage electrode to the piezoelectric element in accordance with the layout of the piezoelectric element, an appropriate polarization process can be applied to the piezoelectric element placed on the stage.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and within the scope of the gist of the embodiment of the present invention described in the claims, Various modifications and changes are possible.

DESCRIPTION OF SYMBOLS 1 Droplet discharge head 4 Inkjet recording apparatus 100 Polarization processing apparatus 101 Wire electrode (corona electrode)
103 Stage 105 Grid electrode 107 Stage electrode 108 Piezoelectric element

JP-A-8-180959

Claims (10)

A polarization processing apparatus that performs polarization processing on a piezoelectric element,
A stage including a plurality of through-holes and mounting the piezoelectric element;
A stage electrode for applying a voltage to the piezoelectric element through the through hole;
A wire electrode for corona discharge to the stage;
A grid electrode facing the piezoelectric element and formed between the wire electrode and the stage electrode;
A polarization treatment apparatus having The polarization processing apparatus according to claim 1, wherein a shape of the opening in the through hole is a hexagon. The polarization processing apparatus according to claim 1, wherein a shape of the opening in the through hole is circular. The polarization processing apparatus according to claim 1, wherein a voltage having a reverse polarity is applied to the wire electrode and the stage electrode. The polarization processing apparatus according to claim 1, wherein a metal rod is inserted into the through hole. The polarization processing apparatus according to claim 5, wherein a voltage having a reverse polarity is applied to the metal rod that overlaps the piezoelectric element and the metal rod that does not overlap the piezoelectric element. The polarization processing apparatus according to claim 1, wherein the through hole is filled with a conductive paste. The polarization processing apparatus according to claim 1, wherein the through hole includes a positioning pin. The polarization processing apparatus according to claim 1, wherein the stage has a temperature adjustment function. Piezoelectric process includes a step of forming a first electrode, a step of forming an electromechanical conversion film on the first electrode, and a step of forming a second electrode on the electromechanical conversion film. Make the device,
A method for manufacturing a piezoelectric element, wherein the piezoelectric element is polarized by the polarization processing apparatus according to claim 1.